The invention discloses an equivalent simulating test piece of gravity drive two-phase fluid circuit consistency. By the application of the equivalent simulating test piece, decomposition process of gravity drive two-phase fluid circuit ammonia at a high temperature and in the condition of using nickel as a catalyst can be equivalently simulated. The equivalent simulating test piece is a closed hollow and integrally-formed gravity thermal pipe and is separated into three sections, namely a liquid storing component, a connecting pipeline and a high temperature baking assembly. By designing the size and structure of the gravity thermal pipe, the equivalent simulating test piece is available for equivalently simulating the decomposition process of the gravity drive two-phase fluid circuit ammonia at the high temperature and in the condition of using nickel as the catalyst, and then obtaining non-condensable gases through ammonia decomposition by adopting a method of measuring non-condensable gases through the gravity thermal pipe, and the measuring method is available and convenient, thereby the consistency of ammonia and the texture of the gravity drive two-phase fluid circuit is effectively and conveniently judged.